A 23-year-old medical graduate from The University of Western Australia with a passion for working with children and mental health issues has been named one of Australia's three Rhodes Scholars at Large.

Katharine Noonan, of Nedlands, who recently completed a Bachelor of Medicine and Bachelor of Surgery (MBBS), said she was inspired to become a doctor after her younger brother was diagnosed with diabetes when he was six.

Katharine is UWA's second Rhodes Scholar this year after Bunbury-born science graduate David Sherwood was named in October as WA's Rhodes Scholar for 2013. The University also produced two Rhodes Scholars last year in medical graduate Vinay Menon (Rhodes Scholar at Large) and medical researcher Rachel Paterson, also of Bunbury.

The University's latest winner plans to undertake a Masters by Research in Psychiatry with the Child and Adolescent Psychiatry section at Oxford University.

Katharine was 2005 Dux of St Hilda's Anglican School for Girls and was awarded the WA Department of Health Prize in Public Heath for the highest mark in fourth-year MBBS in 2012.

She completed her fifth year of studies last year at the Rural Clinical School in Kalgoorlie, where she also volunteered for the Red Cross Soup Patrol and the Western Desert Kidney Health Project, which aims to reduce the high rate of kidney disease in Aboriginal communities in the Goldfields. Katharine also spent a month earlier this year working in paediatrics in Tanzania

"After finishing my studies at Oxford, I want to return to Australia and establish government-funded training programs for professionals in mental health, that reach throughout the country, making psycho-social assistance and medical care more accessible to children and their families," she said.

"Later in my career, I aim to apply my experience by working with the World Health Organisation Mental Health Gap Action Programme to increase delivery of mental health services to low-income countries, where 75 per cent of people do not have access to the treatment they need."

UWA Vice-Chancellor Professor Paul Johnson said Katharine's success was the result of her outstanding ability as well as her great compassion and desire to make a real difference.

"Her success also reflects well on the University's Faculty of Medicine, Dentistry and Health Sciences, which prepares its students to take on a wide range of vital work," Professor Johnson said.

The Rhodes Scholarships are postgraduate awards supporting exceptional all-round students from diverse countries. Established in the will of British-born South African businessman and philanthropist Cecil Rhodes (1852 - 1902), the Rhodes is the oldest and perhaps the most prestigious international scholarship program in the world.

The Rhodes Scholarships aim to nurture leaders for the world's future who are committed to service, and to promote international understanding and peace.

The Rhodes Trust offers nine Rhodes Scholarships in Australia each year, one for each State and three for Australia at large.